U.S. patent application number 13/115214 was filed with the patent office on 2011-12-01 for radio base station and radio resource allocation method.
This patent application is currently assigned to NTT DOCOMO, INC.. Invention is credited to Akihito Hanaki, Kei Kikuiri, Yoshiaki Ofuji, Masashige Shirakabe.
Application Number | 20110292916 13/115214 |
Document ID | / |
Family ID | 44483957 |
Filed Date | 2011-12-01 |
United States Patent
Application |
20110292916 |
Kind Code |
A1 |
Shirakabe; Masashige ; et
al. |
December 1, 2011 |
RADIO BASE STATION AND RADIO RESOURCE ALLOCATION METHOD
Abstract
Provided are a radio packet type determining section that
determines at least whether a radio packet is a first transmission
packet that is allocated persistently at predetermined time
intervals or a retransmission packet among radio packets
transmitted to a radio communication terminal, a first transmission
interval control section that controls a transmission interval of
each first transmission packet so as to disperse the first
transmission packet and a retransmission packet of a radio packet
index different from that of the first transmission packet, a
retransmission interval control section that controls a
transmission interval of each retransmission packet, and a radio
resource allocation section that performs allocation of radio
resources based on the transmission interval of each first
transmission packet and the transmission interval of each
retransmission packet.
Inventors: |
Shirakabe; Masashige;
(Kanagawa, JP) ; Kikuiri; Kei; (Kanagawa, JP)
; Hanaki; Akihito; (Kanagawa, JP) ; Ofuji;
Yoshiaki; (Kanagawa, JP) |
Assignee: |
NTT DOCOMO, INC.
Tokyo
JP
|
Family ID: |
44483957 |
Appl. No.: |
13/115214 |
Filed: |
May 25, 2011 |
Current U.S.
Class: |
370/336 |
Current CPC
Class: |
H04W 72/04 20130101;
H04W 88/08 20130101; H04L 1/1854 20130101; H04L 1/1825 20130101;
H04L 1/1887 20130101; H04L 1/1893 20130101; H04L 1/1861
20130101 |
Class at
Publication: |
370/336 |
International
Class: |
H04W 72/04 20090101
H04W072/04; H04W 72/08 20090101 H04W072/08 |
Foreign Application Data
Date |
Code |
Application Number |
May 28, 2010 |
JP |
2010-123078 |
Claims
1. A radio base station comprising: a radio packet type determining
section configured to determine at least whether a radio packet is
a first transmission packet that is allocated persistently at
predetermined time intervals or a retransmission packet among radio
packets transmitted to a radio communication terminal; a first
transmission interval control section configured to control a
transmission interval of each first transmission packet so that the
first transmission packet and a retransmission packet of a radio
packet index different from that of the first transmission packet
are dispersed in transmission allocation of first transmission
packets allocated persistently at the predetermined time intervals;
a retransmission interval control section configured to control a
transmission interval of each retransmission packet in transmission
allocation of the retransmission packet; and a radio resource
allocation section configured to perform allocation of radio
resources based on the transmission interval of each first
transmission packet determined in the first transmission interval
control section and the transmission interval of each
retransmission packet determined in the retransmission interval
control section.
2. The radio base station according to claim 1, wherein the first
transmission interval control section controls the transmission
interval of each first transmission packet using at least one of
received signal quality of the radio communication terminal, and a
data rate and the radio packet index of the radio packet to
transmit.
3. The radio base station according to claim 2, wherein the
received signal quality includes information on whether or not a
user is a user such that radio packets are allocated to the
predetermined number of consecutive sub-frames, and the data rate
of the radio packet includes information on a data rate required
per certain period in real-time traffic.
4. The radio base station according to claim 1, further comprising:
a control signal generation transmission section configured to
generate a control signal using information output from the radio
resource allocation section, and notifies the radio communication
terminal of the control signal.
5. The radio base station according to claim 1, wherein the first
transmission interval control section sets different transmission
intervals in the transmission allocation of each first transmission
packet to the radio communication terminal.
6. The radio base station according to claim 1, wherein the first
transmission interval control section sets different transmission
intervals in transmission allocation of first transmission packets
to different radio communication terminals.
7. The radio base station according to claim 1, wherein the radio
resource allocation section preferentially allocates the first
transmission packet when transmission timing conflicts between the
first transmission packet and the retransmission packet of the
radio packet index different from that of the first transmission
packet.
8. The radio base station according to claim 1, further comprising:
a maximum number-of-transmission setting section configured to
control the maximum number of transmission times of the
retransmission packet so that transmission timing does not conflict
between the first transmission packet and the retransmission packet
of the radio packet index different from that of the first
transmission packet.
9. The radio base station according to claim 8, wherein the radio
resource allocation section determines transmission intervals of
the first transmission packet and the retransmission packet so as
to maximize the number of transmission times of the retransmission
packet.
10. The radio base station according to claim 8, further
comprising: an MCS determining section configured to control a
modulation scheme and a coding rate of each retransmission packet
so as to decrease a difference in received signal quality between
retransmission packets with the different maximum numbers of
transmission times, based on the maximum number of transmission
times of each retransmission packet determined in the maximum
number-of-transmission setting section.
11. A radio resource allocation method comprising the steps of:
determining at least whether a radio packet is a first transmission
packet that is allocated persistently at predetermined time
intervals or a retransmission packet among radio packets
transmitted to a radio communication terminal; controlling a
transmission interval of each first transmission packet and a
transmission interval of each retransmission packet so that the
first transmission packet and a retransmission packet of a radio
packet index different from that of the first transmission packet
are dispersed in transmission allocation of first transmission
packets allocated persistently at predetermined time intervals and
of the retransmission packet; and performing allocation of radio
resources based on the transmission interval of each first
transmission packet and the transmission interval of each
retransmission packet.
12. The radio resource allocation method according to claim 11,
wherein the transmission interval of each first transmission packet
is controlled using at least one of received signal quality of the
radio communication terminal, and a data rate and the radio packet
index of the radio packet to transmit.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2010-123078, filed on May 28, 2010; the entire contents of which
are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to radio communication control
techniques, and more particularly, to a radio base station and
radio resource allocation method for allocating radio resources to
radio communication terminals at predetermined intervals.
BACKGROUND
[0003] In LTE (Long Term Evolution), OFDMA (Orthogonal Frequency
Division Multiple Access) is used as a downlink modulation scheme,
while SC-FDMA (Single-Carrier Frequency Division Multiple Access)
is used as an uplink modulation scheme. Further, in LTE, high-speed
packet transmissions are realized by using dynamic scheduling for
dynamically allocating radio resources in the time domain and the
frequency domain based on the instantaneous received signal quality
for each sub-frame (for example, 3GPP TS36, 213).
[0004] Meanwhile, in dynamic scheduling it is necessary to transmit
control information for each sub-frame for feedback of received
signal quality, notification of radio resources and the like.
Therefore, when dynamic scheduling is used in packet transmissions
such as VoIP (Voice over IP) in which packet data of a small
payload size periodically occurs, control overhead relatively
increases, and transmission efficiency deteriorates. Thus,
persistent scheduling has been proposed in which radio resources in
the frequency domain are allocated persistently at certain time
intervals (for example, 3GPP, R1-060099).
[0005] FIG. 1 is a diagram showing an example of radio resource
allocation using persistent scheduling. As shown in FIG. 1, in
persistent scheduling, a single or plurality of consecutive
resource blocks in the frequency domain (two consecutive resource
blocks in the frequency domain in FIG. 1) is allocated persistently
to a radio communication terminal at certain time intervals T0. In
persistent scheduling, it is not necessary to transmit the control
information for each sub-frame unlike dynamic scheduling, and it is
thereby possible to greatly reduce control overhead.
[0006] Herein, the resource block is a basic unit of allocation of
radio resources in the frequency domain, and a single resource
block has a bandwidth BW (12 subcarriers) of 180 kHz in the
frequency domain and time length T1 of 0.5 ms in the time domain.
Meanwhile, the sub-frame is a minimum unit of allocation of radio
resources in the time domain, and a single sub-frame has a time
length T2 of 1 ms two times that of a single resource block in the
time domain. Scheduling is performed for each sub-frame in the time
domain, and on a resource-block-by-resource-block basis in the
frequency domain.
[0007] Then, as a method of improving the received signal quality
of a radio communication terminal with poor received signal quality
such that the terminal exists at a cell edge, Sub-Frame Bundling
(SFB) is specified (for example, 3GPP, TS36.321). In Sub-Frame
Bundling, since a single item of packet data that is normally
transmitted in a sub-frame is dispersed over a plurality of
consecutive sub-frames, it is possible to improve the received
signal quality.
[0008] it has also been studied that the above-mentioned persistent
scheduling is performed on a radio communication terminal to which
the aforementioned Sub-Frame Bundling is applied. FIG. 2 is a
diagram showing an example of radio resource allocation using
persistent scheduling for a radio communication terminal to which
Sub-Frame Bundling is applied. As shown in FIG. 2, a plurality of
consecutive sub-frames in the time domain (four consecutive
sub-frames in the time domain in FIG. 2) is allocated persistently
to a radio communication terminal to which Sub-Frame Bundling is
applied at certain time intervals T0. Further, as shown in FIG. 3,
by performing frequency hopping among sub-frames, since frequency
diversity gain is obtained, it is possible to improve the received
signal quality.
[0009] In Sub-Frame Bundling, it is possible to allocate to a
plurality of resource blocks in the frequency domain per sub-frame,
and in transmission for each certain time interval, it is possible
to perform allocation to resource blocks based on any hopping
patterns.
[0010] Further, persistent scheduling is effective scheduling for
the quality of conventional voice speech (for example, voice speech
by AMR at an information rate of 12.2 kbps), and is considered also
effective in high-quality VoIP using CODEC with higher information
rates, TV telephone, bandwidth guaranteed radio transmission
service used in relay of images, etc. To apply to these radio
transmission services, it is required to transmit the data at
information rates higher than the information rates in conventional
voice speech.
[0011] To transmit at high information rates, it is possible to
achieve such transmission by using the method of improving
information rates using MCS (Modulation and Coding Scheme) with
high rates, method of allocating more radio resources in the
frequency domain to users, and the method of allocating more radio
resources in the time domain to users. In uplink, from limitations
of the transmission power of radio communication terminals, the
method is effective of allocating more radio resources in the time
domain to users in the vicinity of the cell edge.
[0012] Thus, it is studied that persistent scheduling is applied to
real-time traffic such as VoIP. As in uplink in LTE, in the case of
applying Synchronous HARQ (Hybrid Automatic Repeat request) in
which transmission of a retransmission packet is performed at
certain time intervals (specifically, an integral multiple of 8
ms), for example, by first applying persistent scheduling and
Sub-Frame Bundling, and allocating more radio resources in the time
domain, it is possible to achieve transmission of real-time traffic
with high information rates.
[0013] However, when the information rate is increased by the
aforementioned means, there is a possibility that a conflict occurs
in transmission timing between a first transmission packet, and a
retransmission packet of a radio packet index different from that
of the first transmission packet. When a conflict occurs in
transmission timing between the first transmission packet and the
retransmission packet, it is not possible to concurrently transmit
the first transmission packet and the retransmission packet to the
same user, and the received signal quality deteriorates in the
radio system.
SUMMARY OF THE INVENTION
[0014] The present invention was made in view of such a respect,
and it is an object of the invention to provide a radio base
station and radio resource allocation method for enabling
reductions of the conflict between transmission timing of a first
transmission packet and transmission timing of a retransmission
packet even when an allocation pattern of resource blocks
persistently allocated at predetermined time intervals is
consecutive in the time domain.
[0015] A radio base station of the invention is characterized by
having a radio packet type determining section that determines at
least whether a radio packet is a first transmission packet that is
allocated persistently at predetermined time intervals or a
retransmission packet among radio packets transmitted to a radio
communication terminal, a first transmission interval control
section that controls a transmission interval of each first
transmission packet so that the first transmission packet and a
retransmission packet of a radio packet index different from that
of the first transmission packet are dispersed in transmission
allocation of first transmission packets allocated persistently at
the predetermined time intervals, a retransmission interval control
section that controls a transmission interval of each
retransmission packet in transmission allocation of retransmission
packets, and a radio resource allocation section that performs
allocation of radio resources based on the transmission interval of
each first transmission packet determined in the first transmission
interval control section and the transmission interval of each
retransmission packet determined in the retransmission interval
control section.
[0016] A radio resource allocation method of the invention can have
the step of determining at least whether a radio packet is a first
transmission packet that is allocated persistently at predetermined
time intervals or a retransmission packet among radio packets
transmitted to a radio communication terminal, the step of
controlling a transmission interval of each first transmission
packet and a transmission interval of each retransmission packet so
that the first transmission packet and a retransmission packet of a
radio packet index different from that of the first transmission
packet are dispersed in transmission allocation of first
transmission packets allocated persistently at predetermined time
intervals and of retransmission packets, and the step of performing
allocation of radio resources based on the transmission interval of
each first transmission packet and the transmission interval of
each retransmission packet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a diagram showing an example of conventional radio
resource allocation;
[0018] FIG. 2 is a diagram showing an example of radio resource
allocation using persistent scheduling for a radio communication
terminal to which Sub-Frame Bundling is applied;
[0019] FIG. 3 is a diagram showing an example of radio resource
allocation using Sub-Frame Bundling in which frequency hopping is
performed;
[0020] FIG. 4 is a diagram illustrating an allocation method in
applying persistent scheduling and Sub-Frame Bundling;
[0021] FIG. 5 is a diagram showing an example of high-quality CODEC
applications;
[0022] FIG. 6 is a diagram showing another example of high-quality
CODEC applications;
[0023] FIG. 7 is a diagram showing examples of conflicts in
transmission timing in non-application of Sub-Frame Bundling;
[0024] FIG. 8 is a diagram showing an allocation method in
application/non-application of Sub-Frame Bundling;
[0025] FIG. 9 is a configuration diagram of a radio communication
system according to an Embodiment of the invention;
[0026] FIG. 10 is a diagram showing an example of a functional
block diagram of a radio base station according to the Embodiment
of the invention;
[0027] FIG. 11 is a diagram showing a first control example in the
radio base station according to the Embodiment of the
invention;
[0028] FIG. 12 is a diagram showing a second control example in the
radio base station according to the Embodiment of the
invention;
[0029] FIG. 13 is a diagram showing a third control example in the
radio base station according to the Embodiment of the
invention;
[0030] FIG. 14 is a diagram showing an example of the functional
block diagram of the radio base station according to the Embodiment
of the invention;
[0031] FIG. 15 is a diagram showing a fourth control example in the
radio base station according to the Embodiment of the
invention;
[0032] FIG. 16 is a diagram showing a fifth control example in the
radio base station according to the Embodiment of the
invention;
[0033] FIG. 17 is a diagram showing an example of the functional
block diagram of the radio base station according to the Embodiment
of the invention;
[0034] FIG. 18 is a diagram showing a sixth control example in the
radio base station according to the Embodiment of the invention;
and
[0035] FIG. 19 is a diagram showing a seventh control example in
the radio base station according to the Embodiment of the
invention.
DETAILED DESCRIPTION
[0036] Described first is a case where an allocation pattern of
resource blocks persistently allocated at predetermined time
intervals is consecutive in the time domain i.e. an allocation
method in applying persistent scheduling and Sub-Frame Bundling
(SFB).
[0037] FIG. 4 shows the case to which is applied Synchronous HARQ
(Hybrid Automatic Repeat request) in which radio packets (herein,
using VoIP packets as an example) of Sub-Frame Bundling transmitted
consecutively in four sub-frames are transmitted at intervals of 20
ms in the time domain, and transmission of retransmission packets
is performed at timing at certain time intervals (for example, an
integer multiple of 8 ms).
[0038] In the case of applying Sub-Frame Bundling and Synchronous
HARQ, since error detection is performed after receiving up to the
final sub-frame on the reception side (base station), some delay
occurs in timing for transmitting ACK/NACK generally as compared
with the case where Sub-Frame Bundling is not applied. Herein, an
example is shown in which retransmission is performed at intervals
of 16 ms by Synchronous HARQ due to the delay of ACK/NACK. In FIG.
4, it is possible to transmit first transmission packets and
retransmission packets of the different radio packet indexes up to
timing of the fifth (.times.4) transmission (the fourth
retransmission-packet transmission) without any conflict, and at
timing of the sixth transmission, another first transmission packet
(VoIP #4) and the retransmission packet (VoIP #1) conflict with
each other.
[0039] Meanwhile, as shown in FIG. 5, by transmitting radio packets
(herein, using VoIP packets as an example) at intervals of 10 ms,
in the case of using CODEC with a high information rate, a first
transmission packet (VoIP #3) transmitted 30 ms later and a
retransmission packet (VoIP #0) conflict with each other at timing
of the third (.times.4) transmission (the second
retransmission-packet transmission). In this case, the maximum
number of transmission times of the retransmission packet
decreases, and the received signal quality (for example, packet
loss rate and throughput) deteriorates.
[0040] In the case of using Synchronous HARQ for transmitting
retransmission packets at intervals of 16 ms, when Sub-Frame
Bundling is applied, intervals of 12 ms are considered (see FIG.
6), as an example of transmission intervals of VoIP packets such
that transmission timing of a retransmission packet does not
conflict with transmission timing of a first transmission packet at
timing of the third (.times.4) transmission (the second
retransmission-packet transmission).
[0041] However, in the case of applying persistent scheduling for
transmitting at intervals of 12 ms, the deterioration is reduced in
characteristics of a user to which Sub-Frame Bundling is applied by
using CODEC with a high information rate. However, when radio
packets are transmitted to another user to which Sub-Frame Bundling
is not applied also at intervals of 12 ms, transmission timing of
the retransmission packet and transmission timing of the first
transmission packet conflict with each other at timing of the
fourth transmission (the third retransmission), and the received
signal quality deteriorates as compared with the case of
transmitting at intervals of 10 ms (see FIG. 7).
[0042] Therefore, in the case of applying persistent scheduling and
Sub-Frame Bundling, the inventor of the invention found out that
there is a possibility that a conflict occurs frequently between
transmission timing of the first transmission packet and
transmission timing of the retransmission packet when first
transmission radio packets are transmitted using transmission
intervals of persistent scheduling persistently as in the
conventional scheme. Further, in the case of applying persistent
scheduling and Sub-Frame Bundling, the inventor of the invention
found out that there is a possibility that a conflict occurs
frequently between transmission timing of the first transmission
packet and transmission timing of the retransmission packet when
the same transmission intervals of first transmission packets are
set on a user to which Sub-Frame Bundling is applied and another
user to which Sub-Frame bundling is not applied (see FIG. 8).
[0043] Then, the inventor of the invention obtained the idea of
controlling transmission timing of first transmission packets and
transmission timing of retransmission packets in the same user
and/or different users, and thereby enabling a conflict in
transmission timing between the first transmission packet and the
retransmission packet to be suppressed even when an allocation
pattern of resource blocks allocated persistently at predetermined
intervals is consecutive in the time domain, and arrived at the
invention.
[0044] An Embodiment of the invention will be described below. In
addition, in the following description of drawings, the same or
similar parts are assigned the same or similar reference
numerals.
[0045] FIG. 9 is a configuration diagram of the radio communication
system according to this Embodiment. As shown in FIG. 9, the radio
communication system is comprised of a radio base station 10, and a
plurality of radio communication terminals (herein, radio
communication terminals 20a and 20b) that perform communications
with the radio base station 10 inside a cell 15 formed by the radio
base station 10.
[0046] The radio base station 10 allocates resource blocks (radio
resources) in the frequency domain and the time domain persistently
(or semi-persistently) to the radio communication terminals 20a,
20b at predetermined time intervals, using a scheduling method (for
example, persistent scheduling) for performing resource allocation
at predetermined time intervals. The radio base station 10 is
capable of transmitting and receiving packet data such as VoIP data
occurring periodically to/from the radio communication terminals
20a, 20b, using resource blocks assigned in each of uplink and
downlink.
[0047] Further, the radio base station 10 is capable of making
allocation patterns of resource blocks in the time domain and the
frequency domain different patterns for each radio communication
terminal in allocating resource blocks to a plurality of radio
communication terminals at predetermined time intervals. For
example, the radio base station 10 is capable of allocating two
consecutive resource blocks in the frequency domain and a single
sub-frame in the time domain to some user (for example, radio
communication terminal 20a) at predetermined time intervals, while
allocating a single resource block in the frequency domain and four
consecutive sub-frames in the time domain to another user (for
example, radio communication terminal 20b) at predetermined time
intervals.
[0048] In addition, in FIG. 9, for convenience in description, only
two radio communication terminals, 20a and 20b, are shown, but the
radio base station is capable of communicating with three or more
radio communication terminals. Further, the radio base station 10
is capable of communicating with a plurality of radio communication
terminals using dynamic scheduling.
[0049] The radio base station 10 according to this Embodiment will
specifically be described below with reference to FIG. 10. The
radio base station 10 is physically an apparatus provided with an
antenna, modem, CPU, memory, etc.
[0050] As shown in FIG. 10, the radio base station 10 has a radio
packet type determining section 101, first transmission interval
control section 102, retransmission interval control section 103,
and radio resource allocation section 104. Further, when the radio
base station 10 performs uplink control, the station 10 is capable
of having a configuration including a control signal generation
transmission section 105.
[0051] The radio packet type determining section 101 has the
function of determining the type of a radio packet to transmit to a
radio communication terminal. As candidates for the radio packet to
transmit, there are a first transmission packet that is transmitted
to the user as the data transmitted for the first time, and a
retransmission packet that is transmitted again at timing
predetermined time later when transmission of the first
transmission packet is lost.
[0052] The first transmission packet includes a first transmission
packet to which is applied scheduling (persistent scheduling) for
allocating radio packets persistently at predetermined intervals,
and a first transmission packet to which is applied dynamic
scheduling. It is only essential that the radio packet type
determining section 10 has the function of determining at least
whether the packet is a first transmission packet that is allocated
persistently at predetermined time intervals, or a retransmission
packet among radio packets transmitted to the radio communication
terminal. And FIG. 10 shows the case where the section 101
determines whether the packet is a retransmission packet, a first
transmission packet to which is applied persistent scheduling, or a
first transmission packet to which is applied dynamic
scheduling.
[0053] When the radio packet determined in the radio packet type
determining section 101 is a first transmission packet of a user to
which is applied persistent scheduling, the section 101 outputs
radio packet transmission interval control information that is
information concerning the transmission interval of persistent
scheduling, and persistent scheduling control information (for
example, information concerning transmission timing in each user,
information concerning transmission RB index and the number of
transmission RBs in each user, etc.) required to control persistent
scheduling to the first transmission interval control section
102.
[0054] When the transmission packet determined in the radio packet
type determining section 101 is a first transmission packet in
dynamic scheduling, the radio packet type determining section 101
outputs dynamic scheduling control information (for example,
received signal quality information such as SINR, instantaneous
throughput information, average throughput information,
transmittable data amount, etc.) that is control information
required in performing dynamic scheduling applied to the base
station apparatus 10 to the radio resource allocation section
104.
[0055] When the transmission packet determined in the radio packet
type determining section 101 is a retransmission packet, the radio
packet type determining section 101 outputs retransmission control
information (for example, information concerning transmission
timing and transmission RB in last allocation, information
concerning the modulation scheme and coding rate in last
allocation, etc.) that is parameters required to perform
retransmission control in applying Synchronous HARQ to the
retransmission interval control section 103.
[0056] The first transmission interval control section 102 controls
the transmission interval of each first transmission packet so as
to decrease the number of conflicts between transmission timing of
a first transmission packet and transmission timing of a
retransmission packet of the radio packet index different from that
of the first transmission packet i.e. so as to disperse the first
transmission packet and the retransmission packet in transmission
allocation of first transmission packets allocated persistently at
predetermined time intervals, and outputs the transmission interval
to the radio resource allocation section 104 as transmission
interval information.
[0057] Further, the first transmission interval control section 102
is capable of controlling the transmission interval of each first
transmission packet in the same user and/or different users, using
at least one of the received signal quality of the radio
communication terminal, and the data rate and the radio packet
index of the radio packet to transmit. In addition, these kinds of
information are included in the radio packet transmission interval
control information received from the radio packet type determining
section 101.
[0058] The retransmission interval control section 103 determines
the transmission interval of the retransmission packet
corresponding to the first transmission packet to output to the
radio resource allocation section 104 as the transmission interval
information.
[0059] The transmission interval information output from the first
transmission interval control section 102 and the retransmission
interval control section 103 is input to the radio resource
allocation section 104. Further, the radio resource allocation
section 104 receives the persistent scheduling control information,
dynamic scheduling control information, and retransmission control
information output from the radio packet type determining section
101.
[0060] The radio resource allocation section 104 determines radio
resource allocation using the transmission interval information
output from the first transmission interval control section 102 and
the retransmission interval control section 103. Further, the radio
resource allocation section 104 outputs the radio resource
allocation result. In uplink, since it is necessary to notify the
radio communication terminal of uplink allocation information (in
semi-persistent scheduling, only the first transmission packet),
the control signal generation transmission section 105 in the radio
base station generates a control signal to notify the radio
communication terminal. In downlink, allocation is performed on the
radio base station based on the radio resource allocation result
without notifying the radio communication terminal. Herein, the
control signal is capable of including an index of a resource block
to assign a radio packet that is the first packet in starting
allocation of persistent scheduling in each user.
[0061] Described next is an example of radio resource allocation
method in the radio base station configured as shown in FIG. 10
described above. In addition, in the following description, an
example is shown where four consecutive sub-frames are allocated to
a user to which Sub-Frame Bundling is applied. However, the
invention is not limited thereto, and it is possible to use any
number of consecutive sub-frames to allocate. Further, with respect
to the retransmission packet in this Embodiment, assuming the
application of Synchronous HARQ in which transmission of the
retransmission packet is performed at timing at certain time
intervals, the example is shown where retransmission is performed
at intervals of 8 ms in user to which Sub-Frame Bundling is not
applied, while retransmission is performed at intervals of 16 ms in
user to which Sub-Frame Bundling is applied. But it is possible to
make the transmission interval of the retransmission packet any
transmission interval. Further, in this Embodiment, in the case of
representing the number of transmission times as "n" in the user to
which Sub-Frame Bundling is applied, it is meant that transmission
is performed in total 4.times.n sub-frames in consideration of the
number of sub-frames consecutively transmitted in Sub-Frame
Bundling.
[0062] FIG. 11 shows an example (first control example) of the
radio resource control in the radio base station 10. In the first
control example as shown in FIG. 11, in allocation of radio
packets, using the radio packet index indicating the transmission
sequence of radio packets, it is set that transmission allocation
intervals of first transmission packets alternately differ from one
another. Herein, shown is the case where the transmission intervals
of first transmission packets are set so that the interval is 8 ms
when the radio packet index is an even number, while being 12 ms
when the radio packet index is an odd number (twice during 20
ms).
[0063] In above-mentioned FIG. 5 in which radio packets are
allocated every 10 ms, in any radio packets, transmission timing
(32 to 36 ms later after the first transmission) of the
retransmission packet in the third transmission (second
retransmission) conflicts with the first transmission packet (30 ms
to 34 ms later) of another radio packet index.
[0064] Meanwhile, by setting as shown in FIG. 11, when the radio
packet index is an odd number, as in the scheme shown in FIG. 5, a
conflict occurs with the first transmission packet of another radio
packet index that is transmitted 30 ms later at timing of the third
transmission (second retransmission). However, when the radio
transmission number is an even number (including "0"), it is
possible to perform transmission without any conflict with the
first transmission packet even at timing of the third transmission
(second retransmission), and as compared with the scheme as shown
in FIG. 5, it is possible to increase the number of transmission
times.
[0065] Thus, in allocation of radio packets, by setting so that the
transmission allocation intervals of first transmission packets
alternately differ from one another in the radio packet index, as
compared with the scheme for setting the transmission allocation
intervals of first transmission packets at a certain value, it is
possible to increase the number of averagely transmittable times,
and to improve the received signal quality.
[0066] FIG. 11 as described above shows the case of the setting
such that the transmission allocation intervals of first
transmission packets alternately differ from one another, but as a
matter of course, the invention is not limited to the case where
the intervals alternately differ from one another in multiples of
"2" i.e. even and odd radio packet indexes, and the transmission
allocation intervals of first transmission packets may be set to
differ from one another in multiples of "3" or more.
[0067] FIG. 12 shows a control example (second control example)
different from the first control example as described above. In the
second control example, radio packet transmission interval control
is performed between users (radio communication terminals)
corresponding to data rates of radio packets.
[0068] FIG. 12 shows the case of performing radio packet
transmission interval control corresponding to data rates of radio
packets, and thereby transmitting first transmission packets at
intervals of 10 ms to a user (radio communication terminal) of a
high information rate, while transmitting first transmission
packets at intervals of 20 ms to a user of a low information rate
(for example, 1/2 rate). By this means, it is possible to achieve
equal received signal quality between users of different
information rates. Herein, the information rate is capable of
including the codec rate in VoIP, and transmission packet size
determined by MCS.
[0069] Further, the above-mentioned first control example may be
applied for each of users of different information rates. For
example, with respect to the user of the high information rate such
that transmission of first transmission packets is performed at
intervals of 10 ms (twice during 20 ms), as shown in FIG. 11 as
described above, it is possible to set transmission intervals of
first transmission packets so that the interval is 8 ms when the
radio packet index is an even number, while being 12 ms when the
radio packet index is an odd number (twice during 20 ms). Further,
with respect to the user of the low information rate such that
transmission of first transmission packets is performed at
intervals of 20 ms, for example, as shown in FIG. 4 as described
above, it is possible to set the transmission allocation intervals
of first transmission packets at a certain value. Thus, by setting
the transmission intervals of first transmission packets for each
user, in each user, it is possible to reduce conflicts between the
first transmission packet and the retransmission packet, and to
improve the received signal quality.
[0070] FIG. 13 shows a control example (third control example)
different from the above-mentioned control examples. In the third
control example as shown in FIG. 13, in allocation of radio
packets, the transmission allocation interval of first transmission
packets is set to be different between the user to which Sub-Frame
Bundling is applied and the user to which Sub-Frame Bundling is not
applied.
[0071] In FIG. 13, with respect to the user to which Sub-Frame
Bundling is applied, first transmission packets are transmitted at
intervals of 12 ms, and with respect to the user to which Sub-Frame
Bundling is not applied, first transmission packets are transmitted
at intervals of 10 ms. Herein, in the user to which Sub-Frame
Bundling is applied, the transmission timing does not conflict with
the first transmission packet up to the third transmission (the
second retransmission) (see FIG. 6), and in the user to which
Sub-Frame Bundling is not applied, it is possible to avoid the
conflict between the first transmission packet and the transmission
timing up to the fifth transmission (the fourth retransmission (see
FIG. 7)). It is thereby possible to improve the received signal
quality of radio packets.
[0072] It is possible to make the determination whether Sub-Frame
Bundling is applied or not applied, for example, by using the
received signal quality such as SINR and propagation path loss.
[0073] As shown in FIG. 8 described above, for each of the user to
which persistent scheduling is applied and the user to which
persistent scheduling is not applied, when first transmission
packets are transmitted at certain transmission intervals (for
example, intervals of 20 ms), it is difficult to reduce conflicts
between the first transmission packet and the retransmission packet
and to improve the received signal quality in both of the users.
Further, when the same transmission interval of first transmission
packets is set on the user to which Sub-Frame Bundling is applied
and the user to which Sub-Frame Bundling is not applied, there is
the problem that the conflict frequently occurs in transmission
timing between the first transmission packet and the retransmission
packet.
[0074] Meanwhile, as shown in FIG. 13, by setting different
transmission allocation intervals of first transmission packets on
the user to which Sub-Frame Bundling is applied and the user to
which Sub-Frame Bundling is not applied, it is possible to reduce
conflicts between the first transmission packet and the
retransmission packet and to improve the received signal quality in
both of the users.
[0075] In addition, the above-mentioned first control example may
be applied for each user. For example, using the received signal
quality, with respect to the user to which Sub-Frame Bundling is
applied, in the case where first transmission packets are
transmitted at intervals 10 ms (twice during 20 ms), as shown in
FIG. 11 described above, it is possible to set the transmission
intervals of the first transmission packets so that the interval is
8 ms when the radio packet index is an even number, while being 12
ms when the radio packet index is an odd number (twice during 20
ms).
[0076] Described next is a radio base station having a
configuration different from that of the radio base station 10 as
shown in FIG. 10 described above.
[0077] A radio base station apparatus as shown in FIG. 14 is
different from the radio base station apparatus as shown in FIG. 10
in the respect that a maximum number-of-transmission setting
section 106 is added. To the maximum number-of-transmission setting
section 106 is input the transmission interval information output
from the first transmission interval control section 102, and the
radio packet transmission interval control information and
persistent scheduling control information output from the radio
packet type determining section 101.
[0078] The maximum number-of-transmission setting section 106
outputs the maximum number-of-transmission upper limit information
using the input information. The maximum number-of-transmission
upper limit information is the maximum number of transmission times
of each retransmission packet enabling the transmission without the
conflict in transmission timing between the first transmission
packet and the retransmission packet of another first transmission
packet of the different radio packet index. Further, the output
maximum number-of-transmission upper limit information is input to
the radio resource allocation section 104. The radio resource
allocation section 104 is capable of determining radio resource
allocation according to the maximum number-of-transmission upper
limit information.
[0079] In FIG. 15, described is a control example (fourth control
example) in the radio base station configured as shown in FIG. 14
described above.
[0080] In the fourth control example as shown in FIG. 15, in
allocation of radio packets, when the first transmission packet
(VoIP #4) conflicts with transmission timing of the retransmission
packet (VoIP #1) of another first transmission packet of the
different radio packet index, the radio resource allocation section
104 preferentially allocates the first transmission packet (VoIP
#4). FIG. 15 shows the case where the transmission allocation
intervals of first transmission packets are set alternately at 8 ms
and 12 ms in allocation of radio packets, but the invention is not
limited thereto.
[0081] In FIG. 5 described above, radio packets are allocated every
10 ms, and in any VoIP packets, the first transmission packet (30
to 34 ms later) conflicts at timing (32 to 36 ms later after the
first transmission) of the third transmission (the second
transmission). Meanwhile, in the first control example as shown in
FIG. 11 described above, when the radio packet indexes indicating
the transmission sequence of radio packets are even numbers
(including "0"), it is possible to perform transmission without the
conflict with the first transmission packet even at timing of the
third transmission (the second retransmission), and as compared
with the conventional scheme as shown in FIG. 5, it is possible to
increase the number of transmission times. Further, when the radio
packet indexes are odd numbers, as in the conventional scheme as
shown in FIG. 5, the conflicts occurs with the first transmission
packet that is transmitted 30 ms at timing of the third
transmission (the second retransmission).
[0082] Accordingly, as shown in FIG. 15, by limiting the number of
transmission times of the retransmission packet (VoIP #1), the
conflict is avoided between the first transmission packet (VoIP #4)
and the retransmission packet, and it is possible to certainly
transmit first transmission packets.
[0083] In addition, by determining the transmission interval of
first transmission packets and the transmission interval of
retransmission packets, the number of transmission times up to the
conflict between the first transmission packet and the
retransmission packet in the user is determined uniquely, and by
the radio resource allocation section 104 limiting the number of
transmission times of the retransmission packet, it is possible to
avoid the conflict with the first transmission packet.
[0084] As shown in FIG. 14 described above, by providing the
maximum number-of-transmission setting section 106, it is possible
to control the maximum number of transmission times of each
retransmission packet so that the transmission timing does not
conflict between the first transmission packet and the
retransmission packet of another first transmission packet. In
addition, in this Embodiment, the maximum number of transmission
times enabling the transmission without any conflict is designated
as the maximum number-of-transmission upper limit.
[0085] FIG. 16 shows a control example (fifth control example)
different from the above-mentioned control examples. In the fifth
control example as shown in FIG. 16, in allocation of radio
packets, the transmission interval of each first transmission
packet is controlled so as to increase the minimum value of the
maximum number-of-transmission upper limit of the retransmission
packet, and the number of transmission times of the retransmission
packet is set.
[0086] For example, when radio packets to which is applied
Sub-Frame Bundling are transmitted twice at intervals of 20 ms
(transmitted over total 8 sub-frames within 20 sub-frames), as
shown in FIG. 16, considered are the transmission method
(transmission pattern 1) of repeating alternately the interval of 8
ms and the interval of 12 ms, and the transmission method
(transmission pattern 2) of repeating alternately the interval of 4
ms and the interval of 16 ms. In addition, the maximum number of
transmission times of each radio packet is assumed to be determined
by the method shown in the fourth control example described
above.
[0087] Herein, in the case of considering the real-time application
such as VoIP, since it is required to control the error rate to
within a certain value within the permissible delay time, it is
possible to improve characteristics by setting the number of
transmission times so as to increase the minimum value of the
maximum number of transmission times of the retransmission packet.
In FIG. 16, the maximum numbers of transmission times are
respectively "2" and "3" in transmission pattern 1, and in contrast
thereto, packets exist such that the maximum number of transmission
times is "1" in transmission pattern 2.
[0088] Therefore, in contrast to transmission pattern 2 where the
maximum number of transmission times is "1", since it is possible
to set the maximum number of transmission times at "2" or more in
transmission pattern 1, it is preferable to select transmission
pattern 1. At this point, the transmission pattern is selected by
the radio resource allocation section 104 to which are input
combinations of a plurality of pieces of transmission interval
information and maximum number-of-transmission upper limit
information.
[0089] Thus, it is possible to improve characteristics by
controlling the transmission interval of each first transmission
packet so as to increase the minimum number of the maximum
number-of-transmission upper limit of the retransmission packet in
allocation of radio packets.
[0090] Described next is a radio base station having a
configuration different from those of the radio base stations 10 as
shown in FIGS. 10 and 14 described above.
[0091] A radio base station apparatus as shown in FIG. 17 is
different from the radio base station apparatus as shown in FIG. 14
in the respect that an MCS determining section 107 is added. The
MCS determining section 107 receives the persistent scheduling
information output from the radio packet type determining section
101 and the maximum number-of-transmission upper limit information
output from the maximum number-of-transmission setting section 106,
and determines a modulation scheme and coding rate using the input
information. As a specific example, since the received signal
quality is determined by the maximum number of transmission times,
it is possible to control so that the packet loss rate is uniform
corresponding to the maximum number of transmission times among the
users.
[0092] Further, it is also possible to select MCS corresponding to
the number of resource blocks allocated per sub-frame, using the
persistent scheduling control information. Herein, when VoIP
traffic is assumed, generally, in speech, a state transition occurs
between two states of the voiced segment and unvoiced segment.
Therefore, to consider variations in the received signal quality,
it is possible to dynamically control the MCS selection criterion
and speech rate (speech CODEC) for each voiced segment. Also in the
case of dynamically controlling the MCS selection criterion and
speech rate, it is possible to apply this Embodiment with ease.
[0093] In FIG. 18, described is a control example (sixth control
example) in the radio base station configured as shown in FIG. 17
described above.
[0094] In the sixth control example as shown in FIG. 18, in
allocation of radio packets, based on the maximum number of
transmission times of each retransmission packet determined in the
maximum number-of-transmission setting section 106, the modulation
scheme and coding rate of each retransmission packet are controlled
so as to decrease a difference in the received signal quality
between retransmission packets with the different maximum numbers
of transmission times.
[0095] FIG. 18 shows the example in the case where the transmission
allocation intervals of first transmission packets are alternately
set at 8 ms and 12 ms in allocation of radio packets. At this
point, when the radio packet indexes in FIG. 18 are even numbers,
it is possible to perform transmission three times, while when the
radio packet indexes are odd numbers, it is possible to perform
transmission up to the second time, and the received signal quality
differs in the case of using the same MCS. Therefore, in this
Embodiment, MCS is determined so that the received signal quality
is almost the same at any transmission timing.
[0096] As a specific example, in radio packets of the even numbers,
transmission is performed using QPSK and R=1/2, and in radio
packets of the odd numbers, transmission is performed using QPSK
and R=1/3. Thus, it is possible to achieve equalization of the
received signal quality by controlling the modulation scheme and
coding rate based on the maximum number of transmission times of
each retransmission packet.
[0097] FIG. 19 shows a control example (seventh control example)
different from the aforementioned control example. The sixth
control example in FIG. 18 described above uses the maximum
number-of-retransmission determining method in consideration of
only the maximum number of retransmission times. In contrast
thereto, the seventh control example as shown in FIG. 19 uses the
maximum number-of-retransmission determining method also in
consideration of the received signal quality (such as, for example,
reception power and reception SINR). As a method of determining the
received signal quality, it is possible to use a result obtained by
measuring the received signal quality for each voiced segment as
information of the received signal quality. By determining the
maximum number of retransmission times also in consideration of the
received signal quality, it is possible to actualize equalization
of the received signal quality effectively, while at the same time
improving throughput.
[0098] The invention is specifically described using the
above-mentioned Embodiment, but it is obvious to a person skilled
in the art that the invention is not limited to the Embodiment
described in the Specification. The invention is capable of being
carried into practice as modified and changed aspects without
departing from the subject matter and scope of the invention
defined by the description of the scope of claims. Accordingly, the
description in the Specification is intended to be an illustrative
explanation and does not have any restrictive meaning on the
invention.
* * * * *